Doc/libamoeba.tex

   1 \chapter{Amoeba Specific Services}
   2
   3 \section{Built-in Module \sectcode{amoeba}}
   4
   5 \bimodindex{amoeba}
   6 This module provides some object types and operations useful for
   7 Amoeba applications.  It is only available on systems that support
   8 Amoeba operations.  RPC errors and other Amoeba errors are reported as
   9 the exception \code{amoeba.error = 'amoeba.error'}.
  10
  11 The module \code{amoeba} defines the following items:
  12
  13 \renewcommand{\indexsubitem}{(in module amoeba)}
  14 \begin{funcdesc}{name_append}{path\, cap}
  15 Stores a capability in the Amoeba directory tree.
  16 Arguments are the pathname (a string) and the capability (a capability
  17 object as returned by
  18 \code{name_lookup()}).
  19 \end{funcdesc}
  20
  21 \begin{funcdesc}{name_delete}{path}
  22 Deletes a capability from the Amoeba directory tree.
  23 Argument is the pathname.
  24 \end{funcdesc}
  25
  26 \begin{funcdesc}{name_lookup}{path}
  27 Looks up a capability.
  28 Argument is the pathname.
  29 Returns a
  30 \dfn{capability}
  31 object, to which various interesting operations apply, described below.
  32 \end{funcdesc}
  33
  34 \begin{funcdesc}{name_replace}{path\, cap}
  35 Replaces a capability in the Amoeba directory tree.
  36 Arguments are the pathname and the new capability.
  37 (This differs from
  38 \code{name_append()}
  39 in the behavior when the pathname already exists:
  40 \code{name_append()}
  41 finds this an error while
  42 \code{name_replace()}
  43 allows it, as its name suggests.)
  44 \end{funcdesc}
  45
  46 \begin{datadesc}{capv}
  47 A table representing the capability environment at the time the
  48 interpreter was started.
  49 (Alas, modifying this table does not affect the capability environment
  50 of the interpreter.)
  51 For example,
  52 \code{amoeba.capv['ROOT']}
  53 is the capability of your root directory, similar to
  54 \code{getcap("ROOT")}
  55 in C.
  56 \end{datadesc}
  57
  58 \begin{excdesc}{error}
  59 The exception raised when an Amoeba function returns an error.
  60 The value accompanying this exception is a pair containing the numeric
  61 error code and the corresponding string, as returned by the C function
  62 \code{err_why()}.
  63 \end{excdesc}
  64
  65 \begin{funcdesc}{timeout}{msecs}
  66 Sets the transaction timeout, in milliseconds.
  67 Returns the previous timeout.
  68 Initially, the timeout is set to 2 seconds by the Python interpreter.
  69 \end{funcdesc}
  70
  71 \subsection{Capability Operations}
  72
  73 Capabilities are written in a convenient \ASCII{} format, also used by the
  74 Amoeba utilities
  75 {\it c2a}(U)
  76 and
  77 {\it a2c}(U).
  78 For example:
  79
  80 \bcode\begin{verbatim}
  81 >>> amoeba.name_lookup('/profile/cap')
  82 aa:1c:95:52:6a:fa/14(ff)/8e:ba:5b:8:11:1a
  83 >>>
  84 \end{verbatim}\ecode
  85
  86 The following methods are defined for capability objects.
  87
  88 \renewcommand{\indexsubitem}{(capability method)}
  89 \begin{funcdesc}{dir_list}{}
  90 Returns a list of the names of the entries in an Amoeba directory.
  91 \end{funcdesc}
  92
  93 \begin{funcdesc}{b_read}{offset\, maxsize}
  94 Reads (at most)
  95 \var{maxsize}
  96 bytes from a bullet file at offset
  97 \var{offset.}
  98 The data is returned as a string.
  99 EOF is reported as an empty string.
 100 \end{funcdesc}
 101
 102 \begin{funcdesc}{b_size}{}
 103 Returns the size of a bullet file.
 104 \end{funcdesc}
 105
 106 \begin{funcdesc}{dir_append}{}
 107 \funcline{dir_delete}{}\
 108 \funcline{dir_lookup}{}\
 109 \funcline{dir_replace}{}
 110 Like the corresponding
 111 \samp{name_}*
 112 functions, but with a path relative to the capability.
 113 (For paths beginning with a slash the capability is ignored, since this
 114 is the defined semantics for Amoeba.)
 115 \end{funcdesc}
 116
 117 \begin{funcdesc}{std_info}{}
 118 Returns the standard info string of the object.
 119 \end{funcdesc}
 120
 121 \begin{funcdesc}{tod_gettime}{}
 122 Returns the time (in seconds since the Epoch, in UCT, as for POSIX) from
 123 a time server.
 124 \end{funcdesc}
 125
 126 \begin{funcdesc}{tod_settime}{t}
 127 Sets the time kept by a time server.
 128 \end{funcdesc}